how to show all layers with hotkey (emulate numpad enabled)
First check that you aren't in local view as this disables the 3Dview layers. When in local view you won't see the layer buttons in the 3Dview header and if you have the view name at the top of the viewport you will see (local) there.

You can find the shortcut settings in the Input Preferences, if you enter layers into the search box you will see a list of actions involving layers with the shortcut keys, clicking the key will allow you to change the shortcut used and then you can click Save User Settings to enable that shortcut each time you start blender.